In eukaryotes, this specific process requires both Rad51 and Dmc1, which are necessary for the formation of Holliday junctions. One step in this process is branch migration. The mule's sterility results from its inability to correctly perform this process, which begins with a small break in the double-stranded DNA at the same point in both chromosomes. For 10 points, name this exchange of base pairs between two similar DNA sequences, a mechanism 
In eukaryotes, this specific process requires both Rad51 and Dmc1, which are necessary for the formation of Holliday junctions. One step in this process is branch migration. The mule's sterility results from its inability to correctly perform this process, which begins with a small break in the double-stranded DNA at the same point in both chromosomes. For 10 points, name this exchange of base pairs between two similar DNA sequences, a mechanism of genetic variation that occurs at the beginning of meiosis.
In eukaryotes, this specific process requires both Rad51 and Dmc1, which are necessary for the formation of Holliday junctions.
{homologous recombination} [or {crossing}-{over}; prompt on meiosis until "break"]